There is nothing more frustrating than forgetting where you parked you car. For this reason, numerous vehicle locator systems have been proposed. Some of these involve the use of cell phones. The problems with existing approaches, however, is that they require significant changes in existing infrastructures.
One example is disclosed in U.S. Pat. No. 6,590,534. The system proposes a small hand-held locator for the automobile operator which will attach to a key chain or fit in a wallet, pocket, or purse. This small portable unit will communicate with a unit attached to an automobile to enable the operator to locate the automobile. Once the portable unit senses that it is leaving the car unit it will request a position estimate from the car unit. The car unit will feed its position information to a modulation circuit which will use the antenna to transmit this information to the handheld unit. The handheld unit has an antenna and a receiver circuit to capture this information. This position estimate will be stored, in both the car unit and the handheld unit, for the duration of the operation and used upon return.
In an alternative embodiment, the portable unit will continuously update its own location independently of the car unit. With this embodiment there is not need for the portable unit to sense that it is leaving the car unit in order to store the car location. The operator can merely push a button to request that the location be stored. Alternatively, the portable unit is the only unit and the car unit is dispensed with altogether. The portable unit would then continuously update the position until the operator signaled that they had parked. The portable unit would then store the parking position. Upon return, the operator must turn on the portable unit. The portable unit will then attempt to acquire a GPS signal to determine position. It will retrieve the car location from memory and calculate a return bearing and display that bearing to the operator. As long as the GPS signal is good it will continue to calculate a return bearing to display to the operator.